1. Field of the Invention
This invention relates to alkali-resistant glass fibres, both in the form of continuous filaments and chopped strands produced therefrom and in the form of non-continuous single filaments, e.g. glass wool. A particular application for such fibres, when in continuous-filament form, is as reinforcement in cementitious products. The invention accordingly also relates to fibre-reinforced cementitious products containing such continuous-filaments fibres.
2. Description of the Prior Art
Owing to the alkaline nature of cement, e.g. ordinary Portland cement, glass fibres for use as reinforcement therein must be resistant to alkalis if they are to retain an adequate degree of strength over long periods. Various proposals have been made in the past few years for glass compositions from which continuous-filament alkali-resistant glass fibres could be drawn. In general, such compositions include a substantial proportion of zirconia (ZrO.sub.2) to provide alkali resistance. A particularly useful range of such compositions is disclosed and claimed in our British Pat. No. 1,290,528. While these known glass compositions generally provide fibres with greatly increased alkali resistance as compared with fibres made from the conventional E-glass used for reinforcing synthetic plastics, they nevertheless exhibit a slow deterioration in strength over long periods in the highly alkaline environment of ordinary Portland cement.